1. Field of the invention
The present invention relates to a disk drive, and particularly, in a magnetic-disk drive, a carriage unit constituting the actuator of the magnetic-disk drive, and a flexible printed circuit (FPC) cable attached to the carriage unit. More particularly, the invention relates to an FPC cable that is provided on its head-side end portion with a pad forming portion on which head pads are formed and a device mounting portion on which electronic devices are mounted which is excellent in noise resisting property, manufacturing cost, electronic device protection property, mounting operability to a carriage, and maintenance.
2. Description of Related Art
An actuator that is provided in magnetic-disk drives has a carriage unit and a voice coil motor (VCM). The carriage unit has a magnetic head mounted thereon and is rotatable over a desired track on the surface of a magnetic disk, and the VCM drives this carriage unit to rotate. The head-side end portion of an FPC cable for data transmission is attached to a carriage constituting the carriage unit, and the head wires from the magnetic head are bonded to the head pad formed on the head-side end portion of the FPC cable. The input/output-side (I/O-side) end portion of the FPC cable is connected to an interface board provided on the bottom surface of the housing of a magnetic-disk drive.
Magnetic-disk drives are becoming higher in density every year. In magnetic-disk drives having four or five 2.5-in or 3.5-in magnetic disks mounted thereon, even noise components due to inductances of head wires and FPC cables become problematic. In order to realize low noise, there is a need to get the mounting position of a preamplifier chip, which amplifies the data read out from a magnetic head, closer to a magnetic head, that is, there is a need to mount the preamplifier chip on the head-side end portion of the FPC cable.
However, if a preamplifier chip is mounted on the head-side end portion of an FPC cable, the pad forming portion for forming head pads will become narrower and therefore the head pad and the spacing between head pads will become smaller. Consequently, it will become difficult to connect head wires to head pads by soldering. In addition, if a supersonic bonding method is employed to bond head wires to head pads, the manufacturing cost will be increased. Furthermore, the wiring of head wires becomes complicated, also a wire from a certain head and a wire from another head need to cross each other, and an angle at which a head wire is pulled out of a wire tube must be made larger. As a consequence, head wire durability becomes worse, bonding operation becomes complicated, and maintenance is reduced. Particularly, in the case where a magnetic head equipped with a magnetoresistive (MR) sensor for reading out data and a thin-film device for recording data is employed, four head wires extend from a single magnetic head and therefore the number of head pads is increased and also the preamplifier chip is increased in size, so that the aforementioned problems become conspicuous.
Also, although there are cases where a preamplifier chip is mounted on the rear surface of a pad forming portion by employing a double-sided FPC or a ceramic substrate, in either case the manufacturing cost will become higher. In addition, since electronic devices, such as preamplifiers, are attached to a rotatable carriage, the protection of these electronic devices must also be taken into consideration. Accordingly, there is a need to provide an FPC cable to address the problems and limitations encountered in the prior art devices.